A user terminal can support simultaneous use of multiple user cards (such as SIM card, USIM card, etc.), and the multiple user cards can work either in a same mode or in different modes. This kind of user terminal is called multi-card multi-mode user terminal.
User terminals always access a network through a mobile communication network. With the rapid development of mobile communication technology, user terminals can access a network through networks other than the mobile communication network. For example, user terminals may access the network through a WiFi network and provide WiFi-based telephony service, i.e., Voice over WiFi (VoWiFi) service. Hereinafter, “networks other than the mobile communication network” are referred to as “other networks”.
User terminals may provide service in different networks through different ways. The same type of service can be implemented in different ways to achieve different performance. For example, voice service can be implemented in a number of different ways. A network working based on an LTE protocol provides voice service through Voice over LTE (VoLTE), which leads to better performance than providing voice service through a way in 2G mode.
Performance of service provided by accessing a network through a mobile communication network is always superior to performance of service provided by accessing a network through other networks. For example, when an LTE network is accessed, voice service is provided through VoLTE; and when a WiFi network is accessed, voice service is provided through VoWiFi, where performance of the former is usually better than that of the latter. However, to the way of accessing a network through a mobile communication network, the performance may be affected by factors, such as signal strength (not limited to signal strength). For example, when the user terminal is located in a remote mountainous area which has relatively narrow mobile communication coverage, service performance of the way of accessing a network through a mobile communication network may be relatively poor. Therefore, in such environment where mobile communication coverage is relatively narrow, service provided by accessing the network through the mobile communication network may have worse performance than similar service provided by accessing the network through other networks.